arc

1. Origins, structure, and basic meaning

• Structure: 弧 has 9 strokes and the on-reading こ. The word 弧 (こ) means an arc or a bow-shaped curve.
• Basic usage: 円弧 (えんこ) means a circular arc; 弧 can describe both a drawn curve and the shape of a rainbow.

2. Common pitfalls and similar expressions

• Drawn arcs and visible curved shapes
  • 円弧を描いた and 弧を描いた both describe drawing an arc. 円弧 explicitly identifies it as a circular arc.
  • 橋は緩い円弧を成している means that the bridge forms a gentle circular arc. 虹が空に大きな弧を作っている describes a rainbow forming a large arc in the sky.